diff options
| author | Vadim Fedorenko <vadfed@meta.com> | 2024-10-01 14:57:14 +0200 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2024-10-04 20:52:19 +0200 |
| commit | 4aecca4c76808f3736056d18ff510df80424bc9f (patch) | |
| tree | 4daf56511a5d5838c9f8628b1409da8353a8fe71 /Documentation/networking | |
| parent | Merge branch 'net-mlx5-hw-counters-refactor' (diff) | |
| download | linux-4aecca4c76808f3736056d18ff510df80424bc9f.tar.xz linux-4aecca4c76808f3736056d18ff510df80424bc9f.zip | |
net_tstamp: add SCM_TS_OPT_ID to provide OPT_ID in control message
SOF_TIMESTAMPING_OPT_ID socket option flag gives a way to correlate TX
timestamps and packets sent via socket. Unfortunately, there is no way
to reliably predict socket timestamp ID value in case of error returned
by sendmsg. For UDP sockets it's impossible because of lockless
nature of UDP transmit, several threads may send packets in parallel. In
case of RAW sockets MSG_MORE option makes things complicated. More
details are in the conversation [1].
This patch adds new control message type to give user-space
software an opportunity to control the mapping between packets and
values by providing ID with each sendmsg for UDP sockets.
The documentation is also added in this patch.
[1] https://lore.kernel.org/netdev/CALCETrU0jB+kg0mhV6A8mrHfTE1D1pr1SD_B9Eaa9aDPfgHdtA@mail.gmail.com/
Reviewed-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Jason Xing <kerneljasonxing@gmail.com>
Signed-off-by: Vadim Fedorenko <vadfed@meta.com>
Link: https://patch.msgid.link/20241001125716.2832769-2-vadfed@meta.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'Documentation/networking')
| -rw-r--r-- | Documentation/networking/timestamping.rst | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/Documentation/networking/timestamping.rst b/Documentation/networking/timestamping.rst index 8199e6917671..b37bfbfc7d79 100644 --- a/Documentation/networking/timestamping.rst +++ b/Documentation/networking/timestamping.rst @@ -194,6 +194,20 @@ SOF_TIMESTAMPING_OPT_ID: among all possibly concurrently outstanding timestamp requests for that socket. + The process can optionally override the default generated ID, by + passing a specific ID with control message SCM_TS_OPT_ID (not + supported for TCP sockets):: + + struct msghdr *msg; + ... + cmsg = CMSG_FIRSTHDR(msg); + cmsg->cmsg_level = SOL_SOCKET; + cmsg->cmsg_type = SCM_TS_OPT_ID; + cmsg->cmsg_len = CMSG_LEN(sizeof(__u32)); + *((__u32 *) CMSG_DATA(cmsg)) = opt_id; + err = sendmsg(fd, msg, 0); + + SOF_TIMESTAMPING_OPT_ID_TCP: Pass this modifier along with SOF_TIMESTAMPING_OPT_ID for new TCP timestamping applications. SOF_TIMESTAMPING_OPT_ID defines how the |